Improved dynamoelectric machines are produced in a myriad of sizes and configurations varying from small, fractional horsepower to extremely large, multiple thousands of horsepower. For purposes of discussion, references will be made here only to integral horsepower alternating current (AC) induction motors which are in the range of about 500 to at least generally about 10,000 horsepower. Machines or electric motors of this power range are generally not custom machines, i.e., they are generally available from a motor manufacturer by specifying required horsepower, shaft RPM and voltage rating. Electrically, however, variations among these three specifiable variables can result in many different arrangements within the motor armature and stator. In addition, since motor speed or shaft RPM is determined by the number of poles, the mechanical structure of the rotor (on which the armature windings are carried) and the stator are varied, not only by the number of poles but also by the physical size of the stator and rotor necessary to support those poles.
Many attempts have been made to overcome the difficulty associated with the many variations in motor arrangements by some form of standardization. U.S. Pat. No. 2,543,131 discusses the standardization problem and addresses the need to provide a terminal block which can facilitate changing from a lower voltage to a higher voltage and from a first speed to a second speed by changing the connections at the block for variations to Delta and Wye connections. However, such an arrangement addresses only a single speed change and voltage change and, while useful, does not address more extensive problems in standardization.
It is desirable, therefore, to provide a machine which incorporates a plurality of features interchangeable between machines of a different size or specification. It is desirable, for example, to provide heating devices which are useable to prevent moisture from condensing into such machines during a cool-down cycle, which devices are applicable to any size machine by varying their number. It is desirable to provide a machine symmetrically constructed with respect to the rotor such that the frame and stator can be positioned in a desired orientation and the rotor inserted with a drive end selectively positioned. It is additionally desirable to provide a frame assembly for a machine in which the orientation of a power conduit box may be selectively changed and in which the location of the power conduit box and an accessory conduit box are variable. It is also desirable to be able to adjust the rotor position in such a machine to align mechanical and magnetic centers.